/* ===================

AX2E (AXESCON XACML 2.0 Engine) is the Java authorization engine, which implements OASIS XACML 2.0 standard.
Copyright (C) 2007 AXESCON LLC

This library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.

This library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
Lesser General Public License for more details.

You should have received a copy of the GNU Lesser General Public
License along with this library; if not, write to the Free Software
Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA


Contact: AXESCON LLC - info{at}axescon.com

 =================== */
package axescon.xacml.engine.fn;

import axescon.xacml.api.*;
import axescon.xacml.model.policy.AttributeValue;

/**
 * @author Date: Sep 28, 2005
 *         Responsibilities: implements basic binary operations
 *         takes two operands of the same type, and return one of the same
 */
public abstract class FnBaseBinaryOp extends AbstractFn implements Fn {

    /**
     * default implementation assumes both args of the same type
     */
    public int getArgTypeListLength() {
        return 1;
    }

    public int getMinArgListLength() {
        return 2;  
    }

    void checkArgs(AttributeValue arg0, AttributeValue arg1) throws FunctionEvalIndeterminateException {
        checkDataTypeAndNull(arg0,0);
        checkDataTypeAndNull(arg1,0);
    }

    public Liquid exec(Liquid[] args) throws FunctionEvalIndeterminateException {
        return new Liquid(exec1(args[0].getSingularUnsafe(), args[1].getSingularUnsafe()));
    }

    public AttributeValue exec(AttributeValue arg0, AttributeValue arg1) throws FunctionEvalIndeterminateException {
        checkArgs(arg0, arg1);
        return exec1(arg0, arg1);
    }

    /**
     *
     * @param arg0 first argument, assumed not null and of right type
     * @param arg1 second argument, assumed not null and of right type
     * @return
     * @throws FunctionEvalIndeterminateException
     */
    abstract AttributeValue exec1(AttributeValue arg0, AttributeValue arg1) throws FunctionEvalIndeterminateException;

    /**
     * checks that arg is of i-th type and not null
     *
     * @param arg
     * @param i
     * @throws FunctionEvalIndeterminateException
     */
    protected void checkDataTypeAndNull(AttributeValue arg,int i)throws FunctionEvalIndeterminateException{

        Class dataType = dataTypes[i];

        assert dataType!=null: "datatype is not set for fn: "+getFnUrn();

        if (arg==null)
            throw new FunctionEvalIndeterminateException("null arg"+i,
                    XacmlException.ERR_CODE_PROCESSING_FN_EMPTY_ARG).setFnUrn(getFnUrn());
        if(! dataType.isInstance(arg))
            throw new FunctionEvalIndeterminateException("arg"+i,
                    XacmlException.ERR_CODE_PROCESSING_FN_BAG_ARG).setFnUrn(getFnUrn());
    }

}
